Liquid crystal display devices are flat display devices which have excellent features such as high definition, low profile, light weight, and low power consumption. In recent years, a market scale of liquid crystal display devices have been rapidly increasing due to improved display performance, increased production capacity, and improved price competitiveness against other display devices.
If a direct current voltage continues to be applied to a liquid crystal layer of such liquid crystal display device for a long time, elements get deteriorated. Therefore, in order to secure a long life of such liquid crystal display device, it is necessary to perform alternating driving (inversion driving) in which the polarity of a voltage to be applied is inverted periodically.
However, in a case where an active matrix liquid crystal display device employs frame inversion driving in which the polarity of a voltage is inverted for every frame, it is inevitable that some unbalance is seen in a plus/minus voltage to be applied to liquid crystal due to various factors such as anisotropy of liquid crystal dielectric constant, variation in pixel potential that is caused by parasitic capacitance between a gate and a source of a pixel TFT (Thin Film Transistor), and a slip of a center value of a counter electrode signal. Consequently, a minor variation in luminance occurs at a frequency that is a half of a frame frequency, making a user see flickers. In order to solve this problem, there is generally employed inversion driving in which pixel signals have opposite polarities between adjacent lines or adjacent pixels as well as voltages are inverted with respect to each frame.
In a case where dot inversion in which the polarity of a voltage is inverted with respect to each pixel is performed, a charging rate of a pixel drops due to signal delay in a data signal line. In order to solve this problem, there is proposed a driving mode in which the polarity of a data signal voltage is inverted for every plural horizontal periods (plural rows). Such a driving mode in which the polarity is inverted for every plural horizontal periods in largely classified into block inversion driving and multi-line inversion driving. The block inversion driving is a mode in which gate lines are divided into blocks and interlace scanning is performed for each of the blocks. The multi-line inversion driving is a mode in which a polarity is inverted every time a plurality of lines are scanned by sequential scanning.